Regional anesthesia refers to anesthetizing only a region of the body, usually in the region where surgery is performed or where acute or chronic pain from any other cause is present. A nerve block accomplishes this task, by administering a local anesthetic agent, such as novocaine, bupivacaine or lidocaine, to the plexus of a nerve. Traditionally, a nerve block was administered using a needle to locate the target nerve and to then insert the anesthetic agent through the needle in order to make contact with the nerve, commonly referred to as a single injection nerve block or single-shot nerve block. One of the major disadvantages of single injection nerve blocks was that the duration of acute pain would be longer than the duration of the single injection nerve block.
As a result, continuous nerve blocks emerged, which utilized an epidural catheter that was threaded through a needle once the needle was properly placed adjacent to the target nerve, and used to deliver variable amounts of the anesthetic agent to the target nerve. In order to properly position the needle on or near the target nerve, a nerve stimulator, such as an electrical current, would be used. Later advances utilized a nerve stimulator on the epidural catheter as well, in order to properly position the epidural catheter on or near the target nerve.
More recently, continuous nerve blocks have been utilized where a needle is properly placed adjacent to the target nerve using ultrasound technology, instead of a nerve stimulator. Subsequent to the proper placement of the needle, an epidural catheter is threaded through the needle and positioned on or near the nerve using a nerve stimulator. However, the major disadvantage to this existing technique is that the catheter is not reliably visible using ultrasound technology, which in turn prevents the epidural catheter to be optimally positioned on or near the target nerve. For example, the current technique requires that the catheter be advanced far down along the nerve to ensure that it is positioned on the nerve for the duration of the continuous block, which in turn may result in coiling of the catheter around the nerve, potentially causing damage to the nerve upon removal of the catheter. In addition, coiling of the catheter is not visible using ultrasound technology, as such technology only allows for a two dimensional view. Furthermore, the current technique requires tunneling of the catheters in order to avoid any dislodgment of the catheters, which also leads to potential damage to the nerves from broken or leaking catheters, as well as infections.
Therefore, there exists a need for a catheter instrument that is visible on an ultrasound image, which would allow for the catheter to be optimally positioned on or near a target nerve and avoid any potential damage from coiling or tunneling of the catheter.